Fluid streams, such as air and liquid, carry contaminant material therein. In many instances, it is desired to filter some or all of the contaminant material from the fluid stream. For example, air flow streams to engines for motorized vehicles or for power generation equipment, gas streams to gas turbine systems, air streams to various combustion furnaces, and air streams to an enclosed environment carry particulate contaminant therein that should be filtered. Also liquid streams in the engine lubrication systems, hydraulic systems, coolant systems, and fuel systems, can carry particulate contaminant that should be filtered. It is preferred for such systems that the fluid streams are free from select contaminant material or have the level of contaminant material therein reduced. A variety of fluid filter (air or liquid filter) arrangements have been developed for contaminant reduction.
In the case of pleated filtration media, the pleat density refers to the number of pleats that can be arranged in a given distance. For a given filtration application, there is often a desired pleat density that maximizes surface area of the filtration media available for filtration and, at the same time, does not contribute to undesired pressure drop across the pleated filtration media as a result of the pleats being too tightly arranged. In addition, it is desirable that the filtration media does not “bunch” or touch because filtration media on adjacent pleat faces that touch becomes “masked media” and masked media is generally not available for filtration. Accordingly, the existence of masking results in loss of filtration surface area. An exemplary prior approach to reduce masking is to use “spacers” for separating the pleat faces. An exemplary disclosure of “spacers” is provided in U.S. Pat. No. 7,625,418.
Pleated media packs formed from corrugated filtration media are disclosed. For example, see U.S. Pat. Publ. No. US 2006/0151382 and U.S. Pat. Publ. No. US 2010/0078379.